The present application is based on Japanese Patent Applications No. 2000-365223, 2000-402883, 2001-54705 and 2001-165068, which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method for manufacturing an optical transmission device composed of a core portion and a clad portion from the photosetting resins. Further, the present invention is relates an optical transmission and reception module to be connected to an optical fiber and its manufacturing method.
2. Description of the Related Art
A conventional technique for forming an optical transmission device at the tip of an optical fiber using the photosetting resins is well known as described in Unexamined Japanese Patent Publication No. Hei. 4-165311, for example. This technique involves forming the optical transmission device by dipping one end of the optical fiber in a photosetting resin solution composed of fluorine monomer and applying a short wavelength laser in the ultraviolet radiation region from the optical fiber to the resin solution.
However, the conventional technique as above had the problem that a core could be only formed, unhardened monomer might stick to the optical transmission device formed, which necessitated a washing process, and the core was formed like a gourd as shown in FIGS. 1 to 3 of the above publication, and could not be formed cylindrically.
Further, a metal cable for transmitting or receiving an electrical signal has been employed for the communication between the devices. The typical metal cable is conformable to the IEEE1394 standard standardized by the IEEE (Institute of Electrical and Electronic Engineers). In this IEEE1394 standard, the Data signal and the Strobe signal relevant to it are transmitted simultaneously.
More particularly, a metal cable 150 conforming to the IEEE1394 standard typically has a 6-pin connector 154 (or alternatively a 4-pin connector) connected at both ends of a cable 152, as shown in FIG. 22. Each pin of the connector 154 (in the order from the first pin to the sixth pin) is supplied with a power source (voltage) from an outside apparatus connected to the connector 154 and the GND to enable four signals of TPA, TPA*, TPB and TPB* to be input or output. A sign xe2x80x9c*xe2x80x9d denotes an inverse signal. On the receiving apparatus, TPA and TPA* are received and either one of them is used as the Data signal, and TPB and TPB* are received and either one of them is used as the Strobe signal.
The cable 152 has internally two pairs of pair signal conductors 156A, 156B that are called an STP (Shielded Twist Pair Cable), a power conductor 158 for supplying an electric power and a ground conductor 160, whereby one cable 152 has a total of six lines. To reduce the influence of noise caused by the electric or magnetic field, the cable 152 has each of the pair signal conductors 156A, 156B twisted and covered with a shield 162A, 162B, and further is covered entirely with a shield 164.
However, in the IEEE1394 standard, the STP is less sufficient to prevent signal deterioration due to the noise, the length of cable being limited to 4.5 m, which means that the STP can not be employed for the long distance connection between the devices.
Therefore, the IEEE1394.b standard for optical transmission is about to be instituted to enable the connection between the remote sites by optically transmitting or receiving the signal. This IEEE1394.b standard is intended for the bi-directional communications, employing two wires.
Also, a technique for the multi-directional communications has been proposed. In this technique, an optical module for enabling the bi-directional communications through the single wire line has been examined.
However, to employ the IEEE1394.b standard to constitute the devices, each device must be equipped with the IEEE1394.b standard, so that the total system is more expensive. Further, if there is the need of making connection to the conventional device conforming to the IEEE1394 standard, each device must be equipped with two standards, so that the cost of the total system is increased.
Since the optical module examined above makes the bi-directional communication through the single wire line, it is necessary to have different light wavelengths for transmission and reception to improve the signal quality. This is required to decrease the cross talk of light. Therefore, the optical module has the higher cost.
The present inventors have made careful researches and found that an effective optical transmission device can be formed by employing two kinds of photosetting resins, and attained the present invention.
Namely, it is an object of the invention to provide a method for manufacturing an optical transmission device with favorable conditions for forming the effective optical transmission device employing two kinds of photosetting resins.
It is another object of the invention to provide a method for manufacturing a self-forming optical transmission device which can be formed in a desired terminal area even if the optical transmission device is deviated from a desired direction.
It is still another object of the invention to provide an optical transmission and reception module and a communication device which can effect stable communications of two relevant signals in simple and inexpensive manner, irrespective of a device-to-device distance.
Further, it is still another object of the invention to provide a method for forming an optical transmission device in which it is unnecessary to make the alignment of optical axis after forming the optical transmission device, and an optical transmission and reception module produced by this method.
In order to accomplish the above object, according to one aspect of the present invention, there is provided a method for manufacturing an optical transmission device including a mixing step for mixing a first photosetting resin comprising a first photopolymerization initiator and a first monomer or oligomer polymerized in a first polymerization type by the first photopolymerization initiator, and a second photosetting resin comprising a second photopolymerization initiator and a second monomer or oligomer polymerized in a second polymerization type that is different from the first polymerization type by the second photopolymerization initiator, a core forming step for forming a core portion of the optical transmission device by hardening the first photosetting resin by making the first irradiation that activates the first photopolymerization initiator but does not activate the second photopolymerization initiator, and a clad forming step for forming a clad portion of the optical transmission device by hardening both the first photosetting resin and the second photosetting resin by making the second irradiation that activates both the first and second photopolymerization initiators, characterized in that the first irradiation has a wavelength shorter than the longest wavelength required to activate the first photopolymerization and longer than the longest wavelength required to activate the second photopolymerization.
The core portion is formed by hardening the first photosetting resin, and the clad portion is formed by hardening each of the first and second photosetting resins, whereby the first photosetting resin after being hardened is required to have a high refractive index than the second photosetting resin after being hardened. Also, in the clad formation step, each of the first and second photosetting resins is hardened, but not copolymerized. After forming the core, if two photosetting resins are both hardened by second irradiation, and the refractive index of hardened mixed resins is lower than before, the clad portion can function. Herein, it is required to activate the first or second photopolymerization initiator at the longest wavelength necessary to cause hardening to form the core portion substantially.
According to another aspect of the invention, there is provided a method for manufacturing an optical transmission device including a mixing step for mixing a first photosetting resin comprising a first photopolymerization initiator and a first monomer or oligomer polymerized in a first polymerization type by the first photopolymerization. initiator, and a second photosetting resin comprising a second photopolymerization initiator and a second monomer or oligomer polymerized in a second polymerization type that is different from the first polymerization type by the second photopolymerization initiator, a core forming step for forming a core portion of the optical transmission device by hardening the first photosetting resin by making the first irradiation that activates the first photopolymerization initiator but does not activate the second photopolymerization initiator, and a clad forming step for forming a clad portion of the optical transmission device by hardening both the first photosetting resin and the second photosetting resin by making the second irradiation that activates both the first and second photopolymerization initiators, characterized in that the first irradiation has an amount of exposure more than the minimum amount of exposure required to harden the first photosetting resin substantially completely and smaller than the maximum amount of exposure not to harden the second photosetting resin completely.
Herein, in the first irradiation, the minimum amount of exposure required to harden the first photosetting resin almost completely means the amount of exposure to cause the extent of hardening sufficient for the core formation, and the maximum amount of exposure not to harden the second photosetting resin completely means the amount of exposure to form the core of a higher refractive index than the refractive index of the clad formed in the clad formation step, viz., the second photosetting resin may be contained by minute quantity in the core portion, if the refractive index of core is not decreased greatly. However, in the first irradiation, it is required that two photosetting resins are not copolymerized.
In the above method for manufacturing the optical transmission device, one of the first polymerization type and the second polymerization type may be radical polymerization, and the other may be cationic polymerization.
In the above method for manufacturing the optical transmission device, when the core of a length L (unit of cm) is formed in a time s (unit of second) employing a light with the wavelength xcexw and the intensity of illumination I0 (unit of mW/cm2), the optical loss xcex1 (unit of dB/cm) of the first photosetting resin before being hardened and the minimum amount of exposure "sgr"A(xcexw) (unit of mJ/cm2) for hardening at the wavelength xcexw may satisfy the following expression:                     α        ≦                              10            L                    ⁢                      log            10                    ⁢                                                    I                o                            ·              s                                                      σ                A                            ⁡                              (                                  λ                  W                                )                                                                        (        1        )            
In the above method for manufacturing the optical transmission device, the first photopolymerization initiator is preferably activated through two photon absorption.
A core can be formed by mixing two kinds of photosetting resins, and hardening a photosetting resin having a higher refractive index alone by light irradiation; and thereafter a clad can be formed by hardening two kinds of photosetting resins at the same time. To allow this technique, light irradiation for forming the core may be made by a wavelength shorter than the longest wavelength required to activate the first photopolymerization initiator, and longer than the longest wavelength required to activate the second photopolymerization initiator. Thereby, an optical module can be easily constituted by combination of a reflection mirror or a half mirror, and a light emitting or light receiving element.
Also, light irradiation to form the core may be made by an amount of exposure more than the minimum amount of exposure required to harden the first photosetting resin substantially completely and smaller than the maximum amount of exposure not to harden the second photosetting resin completely. Thereby, an optical module can be also easily constituted by combination of a reflection mirror or a half mirror, and a light emitting or light receiving element.
Two kinds of photosetting resins may be hardened by combination of radical polymerization and cationic polymerization, whereby two kinds of photosetting resins not causing copolymerization in the first light irradiation process can be easily combined. An example of the photosetting resin hardened by radical polymerization may be a monomer or oligomer having an acryloyl radical or metacryloyl radical, photosensitive polyimide or styrene, or divinylbenzene or unsaturated polyester in combination with the photopolymerization initiator. Also, an example of the photosetting resin hardened by cationic polymerization may be a monomer or oligomer such as epoxy ring, oxetane ring, cyclic ether compound, cyclic lactone compound, cyclic acetal compound, and vinylether compound in combination with the photopolymerization initiator.
Examples of the photopolymerization initiator for radical polymerization may include benzyldimethylketal compounds, xcex1-hydroxyketon compounds, xcex1-aminoketon compounds, bisacylphosphineoxide compounds, metallocene compounds, and other radical photopolymerization initiators.
Examples of the photopolymerization initiator for cationic polymerization may include triarylsulfonium salt compounds, diaryl iodonium salt compounds, metallocene compounds, and other cationic photopolymerization initiators.
In forming the core portion by light irradiation, optical loss of the core portion is important to lengthen the core portion. When the core portion is formed in a length L (unit of cm), if a light with the intensity of illumination I0 (unit of mW/cm7) is supplied from a root of the core portion to the growth end, the intensity of illumination I (unit of mW/cm2) at the growth end can be obtained in accordance with the following expression, assuming that the optical loss of the first photosetting resin before being hardened is xcex1 (unit of dB/cm),                     I        =                              I            0                    ·                      10                          -                                                α                  ⁢                                      xe2x80x83                                    ⁢                  L                                10                                                                        (        2        )            
In order to form a core with the length L (cm) or more in a time s (unit of second) employing a light with the wavelength xcexw, it is required to satisfy the following expression with the minimum amount of exposure "sgr"A(xcexw) (unit of mJ/cm2).                                           σ            A                    ⁡                      (                          λ              W                        )                          ≦                              I            0                    ·          s          ·                      10                          -                                                α                  ⁢                                      xe2x80x83                                    ⁢                  L                                10                                                                        (        3        )            
From the above, the upper limit of optical loss xcex1 before hardening the photosetting resin can be obtained in accordance with the aforementioned expression (1).                     α        ≦                              10            L                    ⁢                      log            10                    ⁢                                                    I                o                            ·              s                                                      σ                A                            ⁡                              (                                  λ                  W                                )                                                                        (        1        )            
That is, the core with the length L (unit of cm) can be formed in a time s (unit of second) under the above conditions.
If the first photopolymerization initiator for forming the core is activated through two photon absorption, a light with longer wavelength can be employed for hardening, and the polymerization with the second photoplymerization initiator can be easily prevented.
The aforementioned manufacturing method can be also said xe2x80x9ca method for manufacturing a self-forming optical transmission devicexe2x80x9d.
Further, according to another aspect of the present invention, there is provided a method for manufacturing a self-forming optical transmission device in which a core portion with almost constant diameter is formed in a passing direction of a light flux of minute diameter, because the light flux is confined within the core portion, when forming continuously the core portion with an increased refractive index by applying the light flux of minute diameter into a photosetting resin to be hardened as aforementioned manufacturing method, to allow the core portion to reach a designed terminal area, a low refractive index structure is disposed to surround a designed formation area, so that the light flux of minute diameter is refracted due to total reflection, if getting rid of the designed formation area.
Also, in the method for manufacturing the self-forming optical transmission device, the terminal area may be a circular area, and the low refractive index structure may form an inner wall on the side face of a truncated cone with the circular area as the upper face.
Also, in the above method for manufacturing the self-forming optical transmission device, the terminal area may be a circle of radius a, and the core portion may be designed to rectilinearly advance at least from a position distance b off a center of the circle of radius a and orthogonal to the terminal area, wherein the inclination angle xcex8m of the side wall of the truncated cone may satisfy the following expression, assuming that the height of the truncated cone is Lm, the refractive index of the core portion with almost constant diameter is n1, and the refractive index of the low refractive index structure is nm,                               0           less than                       θ            m                    ≦                                    tan                              -                1                                      ⁢                                                                                                                              (                                                  b                          +                          at                                                )                                            2                                        -                                          4                      ⁢                                              (                                                  a                          -                          bt                          +                                                                                    L                              m                                                        ⁢                            t                                                                          )                                            ⁢                                              L                        m                                            ⁢                      t                                                                      -                b                -                at                                            2                ⁢                                  L                  m                                ⁢                t                                                    ⁢                  
                ⁢                  t          =                                    tan              ⁢                              xe2x80x83                            ⁢                              θ                max                                      =                          tan              ⁡                              (                                                      cos                                          -                      1                                                        ⁢                                                            n                      m                                                              n                      1                                                                      )                                                                        (        4        )            
Also, in the above method for manufacturing the self-forming optical transmission device, the low refractive index structure may form a part of a spheroid with a major axis as the rotation axis, the terminal area may contain one focal point of an elliptic section with the rotation axis of the spheroid as a major axis, in which the core portion is designed to advance rectilinearly at least from the other focal point.
Also in the method for manufacturing the self-forming optical transmission device, the axes of coordinates are taken in a space, and the terminal area is like a disk of radius a centered at a point (0, b/2, 0) and perpendicular to the y axis, in which the core portion is designed to advance rectilinearly at least from the position of a point (0, xe2x88x92b/2, 0), and assuming that the refractive index of the hardened resin portion of almost constant diameter is n1, the refractive index of the low refractive index structure is nm, the spheroid may be made by rotating a following ellipse with the y axis as a major axis around the y axis as the rotation axis,                                                                                           x                  2                                                  a                  0                  2                                            +                                                y                  2                                                  b                  0                  2                                                      =            1                    ,                      z            =            0                          ⁢                  
                ⁢                              a            0            2                    =                                                    a                2                            +                              a                ⁢                                                                            a                      2                                        +                                          b                      2                                                                                            2                          ⁢                  
                ⁢                              b            0                    =                                    a              +                                                                    a                    2                                    +                                      b                    2                                                                        2                                              (        5        )            
and the following expression may bold at a point on the ellipse of the low refractive index structure,                               cos          ⁢                      {                                                            tan                                      -                    1                                                  ⁢                                                      y                    +                                          b                      2                                                        x                                            -                                                tan                                      -                    1                                                  ⁡                                  (                                                            -                                                                        b                          0                          2                                                                          a                          0                          2                                                                                      ⁢                                          x                      y                                                        )                                                      }                          ≦                              n            m                                n            1                                              (        6        )            
Further, according to another aspect of the invention, there is provided a method for manufacturing a self-forming optical transmission device having a core portion with almost constant diameter in a passing direction of a light flux of minute diameter, because the light flux is confined within the core portion, when forming continuously the core portion with an increased refractive index by applying the light flux of minute diameter into a photosetting resin to be hardened as aforementioned, to allow the core portion to reach a designed terminal area, a reflective structure such as a metal film is disposed to surround a designed formation area, so that the light flux of minute diameter is refracted due to total reflection, when getting rid of the designed formation area.
Also, in the method for manufacturing the self-forming optical transmission device, the terminal area may be a circular area, and the reflective structure may form an inner wall on the side face of a truncated cone with the circular area as the upper face.
Also, in the method for manufacturing the self-forming optical transmission device, the terminal area may be circle of radius a, and the core portion may be designed to rectilinearly propagate at least from a position distance b off a center of the circle of radius a and perpendicular to the terminal area, in which the inclination angle xcex8m of the side wall of the truncated cone satisfies the following expression, assuming that the height of the truncated cone is Lm.                               0           less than                       θ            m                    ≦                                    tan                              -                1                                      ⁢                          {                                                1                                      3                    ⁢                                          L                      m                                        ⁢                    b                                                  ⁢                                  (                                                                                                              s                          6                                                2                                            3                                        -                                          as                      3                                        -                                                                  2                                                  s                          6                                                                    3                                                        )                                ⁢                                  s                  2                                            }                                      ⁢                  
                ⁢                              s            1                    =                                                    -                16                            ⁢                              a                3                            ⁢                              b                3                                      +                          72              ⁢                              ab                3                            ⁢                              L                m                2                                      -                          54              ⁢                              a                3                            ⁢                              L                m                3                                      -                          54              ⁢                              ab                2                            ⁢                              L                m                3                                                    ⁢                  
                ⁢                              s            2                    =                                                    -                4                            ⁢                              a                2                            ⁢                              b                2                                      -                          9              ⁢                              a                2                            ⁢                              L                m                2                                      +                          3              ⁢                              b                3                            ⁢                              L                m                2                                                    ⁢                  
                ⁢                              s            3                    =                                    2              ⁢              b                        +                          3              ⁢                              L                m                                                    ⁢                  
                ⁢                              s            4                    =                                    2              ⁢              b                        -                          3              ⁢                              L                m                                                    ⁢                  
                ⁢                              s            5                    =                                    27              ⁢                              ab                2                            ⁢                              L                m                2                            ⁢                              s                4                                      -                          2              ⁢                              a                3                            ⁢                              s                3                3                                      +                          9              ⁢                              abL                m                            ⁢                                                s                  3                                ⁡                                  (                                                            4                      ⁢                                              a                        2                                                              +                                          bL                      m                                                        )                                                                    ⁢                  
                ⁢                              s            6                    =                                    s              1                        +                                                            4                  ⁢                                      s                    2                    3                                                  +                                  s                  5                  2                                                                                        (        7        )            
Also, in the above method for manufacturing the self-forming optical transmission device, the reflective structure may forms a part of a spheroid with a major axis as the rotation axis, and the terminal area may contain one focal point of an elliptic section with the rotation axis of the spheroid as a major axis, in which the core portion may be designed to advance rectilinearly at least from that the other focal point.
Also, in the method for manufacturing the self-forming optical transmission device, the axes of coordinates are taken in a space, and the terminal area is like a disk with the radius a centered at a point (0, b/2, 0) and perpendicular to the y axis, in which the core portion is designed to advance rectilinearly from the position of a point (0, xe2x88x92b/2, 0), and the spheroid may made by rotating a an ellipse in accordance with the aforementioned expression (5), with the y axis as a major axis around the y axis as the rotation axis,                                                                                           x                  2                                                  a                  0                  2                                            +                                                y                  2                                                  b                  0                  2                                                      =            1                    ,                      z            =            0                          ⁢                  
                ⁢                              a            0            2                    =                                                    a                2                            +                              a                ⁢                                                                            a                      2                                        +                                          b                      2                                                                                            2                          ⁢                  
                ⁢                              b            0                    =                                    a              +                                                                    a                    2                                    +                                      b                    2                                                                        2                                              (        5        )            
In the self-forming optical transmission device, the core portion grows in automatical manner along the traveling direction of light, even if the traveling light is not directed toward the designed terminal area, a structure for modifying the traveling direction of light toward the terminal area, employing the reflection of light is disposed around the designed formation area of the core portion, whereby the traveling direction can be changed toward the terminal area. At this time, if the structure has a lower refractive index than the optical transmission device, or is formed with a mirror face for reflecting the light at any angle, the objects can be accomplished. Such structure may be easily formed like a truncated cone with the terminal area on an upper plane.
Also, if a spheroid in which an ellipse is rotated around a major axis as the rotation axis, with two focal points composed of a point from which at least the core portion is designed to advance rectilinearly, namely, a point from which the reflection, convergence or dispersion of light does not occur, and a center of the terminal area, a light proceeding from the former point (first focal point) is reflected against the spheroid to travel to the latter point (second focal point), thereby producing an ideal structure.
Still further, according to another aspect of the present invention, there is provided an optical transmission and reception module comprising electrical signal input/output means for inputting or outputting a first electrical signal and a second electrical signal relevant with the first electrical signal from or to the outside, conversion means for converting the first electrical signal and the second electrical signal into a first optical signal and a second optical signal, respectively, and inversely converting the first optical signal and the second optical signal into the first electrical signal and the second electrical signal, respectively, first optical signal input/output means for inputting or outputting the first optical signal from or to an optical transmission medium, and second optical signal input/output means for inputting or outputting the second optical signal from or to the same optical transmission medium as the first optical signal at a different wavelength from the first optical signal.
With the optical transmission and reception module according to the above aspect of the invention, when transmitting a signal, the first and second electrical signals are input from the outside by electrical signal input/output means, and converted into the first and second optical signals by the conversion means, respectively. The first optical signal is input into the optical transmission medium such as optical fiber by the first optical signal input/output means, and the second optical signal is made a different wavelength from the first optical signal and input into the same optical transmission medium for the first optical signal by the second optical signal input/output means, the first and second optical signals being transmitted through the same optical transmission medium.
When receiving a signal, the first optical signal is output from the optical signal transmitted through the optical transmission medium by the first optical input/output means, and the second optical signal is output by the second optical signal input/output means. And the first and second optical signals output are inversely converted into the first and second electrical signals by the conversion means, respectively. Then, the first and second electrical signals are output to the outside by the electrical signal input/output means.
That is, in the optical transmission and reception module, to transmit the two relevant electrical signals (first and second electrical signals) input from the outside simultaneously, the first and second electrical signals are converted into first and second optical signals having different wavelengths, respectively, and entered into the same optical transmission medium, while the first and second optical signals having different wavelengths transmitted through the optical transmission medium are inversely converted into the first and second electrical signals, respectively, and output to the outside.
In this way, by optically transmitting a signal, there is no fear for the noise caused by the electromagnetic induction as will occur with the STP, and the optical transmission and reception module is applicable for the connection between remote sites.
Also, the electrical signals are employed for the input or output from or to the outside, and are converted into the optical signals within the communication device, whereby there is no need of providing the special equipment for the communications between the devices employing the conventional metal cable, resulting in the reduced costs for using this communication device.
Also, in the above optical transmission and reception module, the second optical signal input/output means preferably comprises synthesis and separation means for synthesizing two optical signals having different wavelengths that are output from the first optical signal input/output means and the second optical input/output means to input a synthesized signal into the optical transmission medium, and separating the two optical signals having different wavelengths transmitted through the optical transmission medium.
With the aforementioned optical transmission and reception module, the second optical signal input/output means uses the synthesis and separation means to synthesize the first and second optical signals having different wavelengths to enter a synthesized signal into the optical transmission medium, when transmitting a signal, while separating a signal transmitted through the optical transmission medium into the first and second optical signals, when receiving the signal. Thereby, the communications of the first and second optical signals via the same optical transmission medium can be simply provided. Such synthesis and separation means can be implemented by employing a wavelength filter, for example.
Further, there is provided the optical transmission and reception module, further comprising guide and separation means for guiding an optical signal for input into the optical transmission medium to the optical transmission medium, and separating an optical signal for output from the optical transmission medium, the guide and separation means being provided on at least one of the first optical signal input/output means and the second optical signal input/output means.
Also, the guide and separation means provided at least one of the first and second optical signal input/output means can guide an optical signal for input into the optical transmission medium from the corresponding optical signal input/output means into the optical transmission medium, when transmitting the signal, or separates the optical signal for output from the optical signal medium to output the signal, when receiving the signal.
In the optical transmission and reception module, wherein the electrical signal prefconforms to the IEEE1394 standard.
The optical transmission medium preferably can be employed as a substitute for the 1394 standard metal cable, because the electrical signals (first and second electrical signals) conform to the IEEE1394 standard.
The optical transmission and reception module preferably comprises connection means for connecting the optical signal to the optical transmission medium so that the optical signal can be input or output from or to the optical transmission medium.
In the above optical transmission and reception module, the connection means is employed to connect with the optical transmission medium so that the optical signals (first and second optical signals) can be input or output from or to the optical transmission medium. For example, when the distance between the external devices making the communications employing the communication device is changed, it is only necessary to change the optical transmission medium to the length corresponding to the changed distance.
Also, a communication device in which the optical transmission and reception module is preferably provided at either end of the optical transmission medium.
The optical transmission medium can be simply employed as a substitute for the conventional metal cable, because the optical transmission and reception module is provided at either end of the optical transmission medium, and integrally formed.
Furthermore, according to a still another aspect of the present invention, there is provided a method for forming an optical transmission device within an optical transmission and reception module for transmitting and receiving an optical signal, the optical transmission and reception module having internally a light emitting element for emitting a light beam for communication with a predetermined wavelength and a light receiving element for receiving the light beam, characterized by including introducing a light beam of a predetermined wavelength for formation of the optical transmission device into a space area for forming the optical transmission device within the optical transmission and reception module to fill a photosetting resin solution that is hardened in an optical axis direction, inserting one end of an optical fiber through a light input/output opening of the optical transmission and reception module, outputting the light beam of predetermined wavelength for communication by emitting light from the light emitting element, detecting a quantity of output light output to the outside of the transmission and reception module via the optical fiber among the light beam of predetermined wavelength for communication that is output, adjusting a light input/output axis direction of the optical fiber such that the quantity of output light is almost at maximum, and entering the light beam of predetermined wavelength for formation of the optical transmission device from the other end of the optical fiber into the optical transmission and reception module, while maintaining the adjusted light input/output axis direction of the optical fiber.
With the above aspect of the invention, the photosetting resin solution is filled in the space area for forming the optical transmission device within the optical transmission and reception module, and one end of the optical fiber is inserted through the light input/output opening of the optical transmission and reception module, and then the light emitting elements are caused to emit light. Thereby, the light beam of predetermined wavelength for communication is passed through a predetermined path within the optical transmission and reception module to proceed toward the light input/output opening to be incident upon one end face of the optical fiber, and output via the optical fiber to the outside of the optical transmission and reception module. And the light input/output axis direction of the optical fiber is adjusted so that the quantity of output light is almost at maximum, while detecting the quantity of output light.
After this adjustment, a light beam of predetermined wavelength for formation of optical transmission device is entered from the other end of the optical fiber to the optical transmission and reception module, while maintaining the adjusted light input/output axis direction of the optical fiber, so that the light beam for formation of the optical transmission device is introduced into the photosetting resin solution to form the optical transmission device, whereby the light beam can be transmitted at almost maximum efficiency in the optical transmission device formed. Accordingly, it is possible to omit the operation of making the alignment of the optical axis of the light emitting or receiving element in the optical transmission and reception module with respect to the optical transmission device formed.
Also, in the above method for forming the optical transmission device, it is preferable that the photosetting resin solution is a mixture solution of a first photosetting resin solution having a longer setting start wavelength than the predetermined wavelength and a second photosetting resin solution having a shorter setting start wavelength than the predetermined wavelength, wherein an axial core portion is formed by hardening only the first photosetting resin solution with the light beam of predetermined wavelength from the light source, and then a clad portion having a smaller refractive index than that of the core portion is formed around the core portion by applying light in a wavelength band for hardening the first and second photosetting resin solutions from around the mixture solution. Consequently, a so-called step index type optical transmission device having the core portion and the clad portion can be formed.
Also in the above method for forming the optical transmission device, it is preferable that the optical transmission device is produced in a state where one end of the optical fiber is immersed in the photosetting resin solution. Thereby, the optical transmission device is formed in a state of connecting it with one end of the optical fiber, and the optical fiber is fixed by the formed optical transmission device, without causing misalignment between the optical fiber and the optical transmission device that are coupled.
Since the optical transmission device is internally formed by the above method, the optical beam can be transmitted at almost maximum efficiency without making the alignment of optical axes for the light emitting and receiving elements after forming the optical transmission device. That is, the optical transmission and reception module with less optical loss and that is efficient can be produced simply.
Further, there is provided an optical transmission and reception module, comprising electrical signal input/output means for inputting or outputting a first electrical signal and a second electrical signal related with the first electrical signal from or into the outside, conversion means for converting the first electrical signal and the second electrical signal into a first optical signal and a second optical signal, respectively, and inversely converting the first optical signal and the second optical signal into the first electrical signal and the second electrical signal, respectively, first optical signal input/output means for inputting or outputting the first optical signal from or into an optical fiber, second optical signal input/output means for inputting or outputting the second optical signal from or into the same optical fiber for the first optical signal at a different wavelength from the first optical signal, and light propagating means having an optical transmission device formed by the above method for forming the optical transmission device between the optical fiber and the first optical signal input/output means, and between the optical fiber and the second optical signal input/output means.
With the optical transmission and reception module as described above, two relevant electrical signals (first electrical signal and second electrical signal) input from the outside are transmitted simultaneously, converted into the optical signals having different wavelengths (first optical signal and second optical signal) by the conversion means, and entered into the same optical fiber by the first optical signal input/output means and the second optical signal input/output means. Also, the optical signals having different wavelengths (first optical signal and second optical signal) transmitted via the optical fiber are inversely converted into the electrical signals (first electrical signal and second electrical signal) and output to the outside.
Thus, there is no fear for the noise caused by the electromagnetic induction by transmitting the optical signal, whereby the stable communication is enabled, irrespective of the device-to-device distance. Specifically, the optical transmission and reception module can be employed for the communication conforming to the IEEE1394 standard. Also, the electrical signals are input or output from or to the outside, and converted into the optical signals within the communication device. Therefore, the optical transmission and reception module can be applied to the communications between the devices employing the conventional metal cable, without needing any special equipment, and can be utilized without increasing the costs.
Also, the optical transmission and reception module preferably comprises the light propagating means having the optical transmission device formed by the above method for forming the optical transmission device according to the invention between the optical fiber and the first optical signal input/output means, and between the optical fiber and the second optical signal input/output means, whereby the first and second optical signals can be input or output from or into the optical fiber efficiently by the light propagating means and transmitted or received via the optical fiber to or from the outside.
In this case, it is preferable to have a so-called Pig-Tail type in which the other end of the optical fiber is extended a predetermined length from the housing of the optical transmission and reception module for the connection with the external apparatus.
Also, in the above optical transmission and reception module, it is preferable that the second optical signal input/output means comprises synthesis and separation means for synthesizing two optical signals having different wavelengths that are output from the first optical signal input/output means and the second optical signal input/output means to enter a synthesized signal into the optical fiber, and separating two optical signals having different wavelengths that are transmitted through the optical fiber.
In this way, the second optical signal input/output means comprises the synthesis and separation means to synthesize the first optical signal and the second optical signal that have different wavelengths to be input into the optical fiber, when transmitting the signal, or separate the synthesized signal transmitted through the optical fiber into the first optical signal and the second optical signal in receiving the signal. Accordingly, the communications of the first optical signal and the second optical signal via the same optical fiber can be simply provided. This synthesis and separation means can be implemented employing the wavelength filter, for example.
Also, the above optical transmission and reception module preferably further comprises guide and separation means for guiding an optical signal for input into the optical fiber to a light transmission medium and separating an optical signal for output from the optical fiber, the guide and separation means being provided on at least one of the first optical signal input/output means and the second optical signal input/output means.
Thereby, owing to the guide and separation means provided on at least one of the first optical signal input/output means and the second optical signal input/output means, the optical signal for input into the optical fiber that is passed from the corresponding optical signal input/output means is guided into the optical fiber, when transmitting the signal, or the optical signal for output from the optical fiber is separated and output (received), when receiving the signal. Accordingly, the optical signal for input can be entered into the optical fiber efficiently, and the optical signal for output from the light transmission medium can be received efficiently by the output section, reducing the optical loss (LOSS).
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.